Light emitting diodes (LEDs) are widely applied in the fields of display screens, backlights and special lighting. As shown in FIG. 1, an LED epitaxial wafer, as a core of an LED, may comprise a substrate 101, a buffer layer 102, an n-type semiconductor layer 103, a light emitting layer 104, an electron barrier layer 105 and a p-type semiconductor layer 106. The light emitting layer 104 may be disposed between the n-type semiconductor layer 103 and the p-type semiconductor layer 106 to form PN junctions. Conventionally, an LED chip may comprise the LED epitaxial wafer mentioned above, a current diffusing layer 107, a p-type electrode 108 and an n-type electrode 109.
Sapphire may be a conventional material for forming the substrate. The LED epitaxial wafer may be manufactured in a metal organic chemical vapor deposition device, using high purity hydrogen and nitrogen as carrier gas, and using high purity trimethyl gallium, trimethyl indium and ammonia as the Ga, In and N sources, respectively. The manufacturing method may comprise the steps of: forming a buffer layer on a substrate; forming an n-type gallium nitride layer on the buffer layer; forming a light emitting layer on the n-type gallium nitride layer, where the light emitting layer is an InGaN multi-quantum well layer; forming an electron barrier layer on the light emitting layer; and forming a p-type gallium nitride layer on the electron barrier layer.
The epitaxial wafer for the LED mentioned above may be a single wafer, that is, only one surface of the substrate may be used to form an LED epitaxial structure. It is a tremendous waste for LED manufacturing.